With development of USB (Universal Serial Bus) interface technology, a user can use a connection line to connect the USB interfaces of two terminals, achieving data interaction or power transfer between terminals.
After connecting two terminals with the connection line, the master device of the two terminals can read/write data form/to the slave device through the connection line, while the slave device cannot read/write data form/to the master device. After connecting two terminals with the connection line, the master and slave states of the two terminals are random and cannot be switched, which is not good for data interaction between the terminals.